1. Field of the Invention
The present invention relates to the upgrading of petroleum residium (petroleum resid), bitumen and/or heavy oils by the removal therefrom of heavy, high molecular weight multi-ring aromatics and metals present in such petroleum resid, bitumen, shale oil and/or heavy oils in the form of asphaltenes and/or heavy resins and/or polycyclic hetero (N) aromatics.
2. Description of the Related Art
Heavy, high molecular weight multi-ring aromatics, polycyclic hetero (N,S,O) aromatics and metals-containing molecules, e.g., porphyrins, are present in petroleum resid, bitumen and/or heavy oils largely in the form of a solubility class called asphaltenes or, depending on the feed, as individually identifiable molecular types, e.g., the asphaltene can comprise a mixture of such materials, or materials such as polycyclic hetero atom(N,S,O)-containing aromatics can be present per se, in such feeds.
The asphaltene fraction present in such feeds contains the most polar molecules. Traditionally, to force such asphaltene materials out of the petroleum resid, bitumen and/or heavy oils, a process known as solvent deasphalting is practiced. In that process, an excess of non-polar solvent is added to the petroleum resid, bitumen and/or heavy oils (hereinafter collectively referred to as heavy hydrocarbon feed stream) to force the polar asphaltene material out of the heavy hydrocarbon feed stream. Current commercial deasphalting processes use liquid propane or liquid butane as the non-polar precipitation inducing solvent. Such processes are energy intensive requiring the refrigeration and compression/pressurization of the propane or butane to condense them into a liquid. Following the removal of the precipitated asphaltene from the now deasphalted heavy hydrocarbon feed stream containing the liquid propane or butane, the propane or butane is recovered by evaporation from the heavy hydrocarbon feed stream, necessitating the re-refrigeration and re-pressurization of the now gaseous propane or butane for re-condensation into liquid form for re-use. Another drawback of solvent deasphalting, in addition to the high energy costs involved, is the lack of selectivity in the solvent deasphalting process. The lack of selectivity of the solvents is evidenced by the co-precipitation of non-asphaltenic molecules along with the asphaltenes and the presence of residual asphaltene molecules in the deasphalted oil (DAO) fraction.
Alternatively, petroleum resid can be visbroken, coked or used as residual sulfur fuel oil (RSFO) or as asphalt without removal of the asphaltene fraction. Such processes are also either energy intensive, expensive or wasteful of high value hydrocarbons present in the petroleum resid feed stream.
More desirable, however, are processes such as the solvent deasphalting previously described, which, following removal of the asphaltene fraction, produce a deasphalted oil (DAO) which has a higher value and is of higher quality residual sulfur fuel oil (RSFO) or as feedstock for fluid catalytic cracking (FCC) to force higher value liquids which could not be otherwise secured from the petroleum resid per se. The recovered asphaltene fraction is currently processed via high temperature thermal chemistry (coking and/or visbreaking) to form slightly higher value liquids and coke, or it is used as feedstock for asphalt production.
It would be highly desirable to develop a process for the removal of the heavy, high molecular weight multi-ring aromatics and/or resins and/or polycyclic hetero atom(N,S,O)-containing aromatics (hereinafter collectively referred to a asphaltenes unless otherwise indicated) from petroleum resid, bitumen and/or heavy oils, which is less energy intensive, e.g., uses little or no solvent, and is more selective.